Checkbook calculator



FIG. 1 is a front, top and left perspective view of a checkbook calculator showing my new design; the broken line showing of a checkbook is environmental only and forms no part of the claimed design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is rear elevational view thereof;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof;

FIG. 6 is a right elevational view thereof; and,

FIG. 7 is a left elevational view thereof. 

The ornamental design for a checkbook calculator, as shown and described. 